at 1.2k as advertised on luthermusic? all are overpriced, esp the XP30 and SY99. buying for your studio rental services?
anyway, just between these three, get the korg triton LE. yamaha SY99 is a bit dated and also hard to use, and the LCD screen can be quite hard to see under certain lighting. at least the korg is a more common keyboard, most keyboardists will be familiar with korg user interface. lightweight too, if carrying around for gigs. and a good bright backlit screen. sounds and touch aren't too great though.
if left to my choice, with that money, i'd actually hunt around for a used motif6, or EX5 or EX7 synth, or triton classic, trinity V3, to name a few.